Trolley wheel assembly

ABSTRACT

A trolley includes a front wheel assemblie ( 12 ) and a rear wheel assembly both assemblies mounted on a trolley frame. The front wheel assembly ( 12 ) includes a fixed wheel assembly ( 24 ) to aid control of the trolley. In one form the front wheel assembly ( 12 ) includes a pair of swivel castors ( 18 ) and a fixed wheel assembly ( 24 ) disposed between the castors ( 18 ). The front wheel assembly ( 12 ) is designed so that when the castors ( 18 ) swivel from their orientation for forward travel, the fixed wheel assembly ( 24 ) is caused to be lifted off the ground. The trolley also includes a camming device which is operative to lift the front wheel assembly ( 12 ) off the ground when the trolley is moved into a nested configuration with a like trolley.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of International application No.PCT/AU02/00388, filed Mar. 28, 2002, which in turn claims priority toAustralian patent application No. PR 4245, filed Apr. 5, 2001; PR 4621,filed Apr. 26, 2001, PR 8757, filed Nov. 8, 2001 and PS 0584, filed Feb.15, 2002.

TECHNICAL FIELD

The present invention relates to a trolley and in particular, in oneaspect, to a trolley with a modified wheel assembly to aid in control ofthe trolley. The invention has been designed especially, but notexclusively, for use in shopping trolleys and the invention is hereindescribed in that context. It is to be appreciated however that theinvention is not limited to that use.

BACKGROUND OF THE INVENTION

Shopping trolleys are typically configured with four fully swivellingcasters, one caster being provided at each corner of the base of thetrolley frame to form front and rear wheel assemblies. The use of fourfully swivelling casters enables the shopping trolley to be manoeuvredforwards or sideways, however can render the trolley difficult tocontrol, with steering a trolley around a corner or maintaining it in astraight path or on a sloped surface being particularly difficult. Withthe casters being free to swivel and therefore not providing anysideways resistance, altering the path of the trolley requires theoperator to impart a moment directly on the trolley to rotate it asthere are no fixed wheels about which the trolley can easily rotate. Thedifficulty in maneuvering a trolley is increased when loaded withshopping, with the increased weight resulting in an increased momentbeing required to alter the path of the trolley.

The applicant has found that a shopping trolley having the front pair ofwheels fixed from swivelling, with the wheel axles in a co-axialrelationship, and the rear wheels being able to swivel, not unlike amotor vehicle, is easier to manoeuvre. A trolley with such aconfiguration is able to pivot about the fixed set of wheels to alterits direction. The operator need only control this pivoting about thefixed wheels by applying a small sideways force to the trolley handle todirect the trolley along the required path.

Whilst this arrangement is effective, the manoeuvrability of a trolleymay be unduly limited, particularly when turning the trolley in tightsituations.

SUMMARY OF THE INVENTION

In one aspect, the invention is directed to a trolley comprising atrolley frame, and front and rear wheel assemblies, one of said wheelassemblies including a pair of casters, each including a yoke mounted tothe trolley frame in a manner that allows the caster to swivel about afirst axis, and a caster wheel mounted to the yoke so as to be rotatableabout a second axis which is transverse to said first axis, each casterbeing operative to adopt a first orientation for forward travel of saidtrolley, the one wheel assembly being configured so as to lift thetrolley frame when the casters swivel about their first axes from thefirst orientation, and a fixed wheel including at least one wheel whichhas an axis of rotation which is orientated so that said fixed wheelassembly assists in maintaining directional control of said trolley inits forward travel, the wheel of the fixed wheel assembly beingpositioned to engage the ground when the castors are in the firstorientation and to be off the ground when the trolley frame is lifted byswivelling of the casters about their first axes.

In one form, the fixed wheel assembly is located between the casters.

In one form, the wheels of fixed wheel assembly and the casters in theirfirst orientation are designed to engage the ground. In thisarrangement, the fixed wheel assembly provides the directional controlfor the trolley, whilst the casters which are able to swivel provide thelateral stability for the trolley to prevent tipping.

In another form, the wheel of fixed wheel assembly is designed toproject below the level of the caster wheels when in their firstorientation so that, in forward travel, the trolley is supported at saidone wheel assembly by the fixed wheel assembly. The casters which may befixed or swivelling, act as outrigger wheels to prevent sideways tippingof the trolley.

In this latter arrangement, preferably the fixed wheel assembly includesa plurality of closely spaced wheels to provide more balanced support atthe front of the trolley.

The arrangement of the invention has significant advantages. Byproviding a central fixed wheel, enables the trolley to be manoeuvredmore easily than is the case if the fixed wheels are widely spacedapart. Further, it provides a system which can be easily andinexpensively retrofitted to existing trolleys. It also maintains auseful purpose for the existing casters to enable the trolley to bestably supported. In particular, the arrangement enables the trolley tomeet some government requirements whereby a trolley must be suppliedwith at least four wheels.

In a particular embodiment, the caster wheel in each caster is offsetfrom its first axis so that, in use, the caster wheel swivels about anarc around its first axis. In addition, preferably the caster is mountedto the trolley frame with the first axis inclined to the vertical sothat in use, on swivelling of the casters about their respective firstaxes, the vertical displacement of the centre of the respective castersfrom a fixed point on the trolley varies.

In one form, each caster is mounted to the trolley so that this verticaldisplacement is at a minimum when that caster is in its firstorientation. This arrangement has particular advantage in that wheneither of the casters is caused to be angularly spaced about its firstaxis from the first orientation by a predetermined amount, that casterwheel is lower than the fixed wheel thereby lifting the fixed wheel offthe ground. The degree of angular displacement required to provideadequate clearance to fully lift the fixed wheel off the ground willdepend on the specific configuration of the wheel assembly, but theapplicant has found that displacement of 10-20 degrees from the firstorientation is ideal. Further, if the casters are operative to remain incontact with the ground at all times, they can be caused to swivel fromthe first orientation (and thereby lift the fixed wheel off the ground)simply by applying a sideways force to the trolley. This arrangement hasthe advantage that the fixed wheel assembly assists in controllingforward movement of the trolley, but does not inhibit sideways movementof the trolley as the caster wheels, as they pivot, would be caused tolift this fixed wheel assembly off the ground. In addition, the fixedwheel can inhibit the trolley inadvertently “running away” when it isstationery as it lessens the tendency to move sideways if parked on asideways sloping surface.

In one arrangement, the novel wheel assembly may be retrofitted to anexisting trolley assembly by securing a fixed wheel assembly to thetrolley body. This may be secured to the existing cross bar supportingthe caster wheel assemblies or an additional cross bar may be installed.Further, the casters may be arranged to have their axes inclined to thevertical in the desired orientation merely by tilting the trolley framewhich can be simply achieved by placing larger casters on the rear wheelassembly. Alternatively the caster swivel axis may be inclined by theaddition of an appropriately tapered spacers mounted at the point ofattachment of the caster to the trolley.

In another form, an elongate rigid member is used to interconnect theframes of the caster wheel assemblies. In this latter arrangement,preferably the elongate member is used as the axle for the fixed wheelassembly. Appropriate spacers, or fixtures are provided on the axle toproperly locate those fixed wheels in place.

In one form of this latter arrangement, the elongate member extendsthrough the frame axles of the respective casters. Further, the casterwheels from the pair of assemblies are removed and are used as part ofthe fixed wheel assembly. In their place, smaller outrigger wheels areused. The advantage of this arrangement is that the caster wheels aredesigned to be constantly in contact with the ground. As such, they areideally suited to be used as the fixed wheel assembly. Further as theoutrigger wheels are only used to prevent tipping of the trolley, aninferior wheel may be used as compared to the caster wheels, therebyfurther reducing the cost of retrofitting.

In yet a further aspect, the invention is directed to a method ofretrofitting a trolley using any one of the techniques described above.

In a particularly preferred form, the front wheel assembly includes thefixed wheel assembly. In this arrangement preferably the rear wheelassembly includes pivoting casters, although other arrangements may beused.

Whilst the design of the shopping trolley with a fixed wheel as part ofthe front wheel assembly aids control of an individual trolley, it mayimpede the manoeuvrability of the trolleys when in a nestedconfiguration as a train as it significantly restricts the ability to beable to change the direction of the train of trolleys.

Accordingly to a further aspect, the present invention provides atrolley including a trolley frame, and front and rear wheel assembliesmounted on said trolley frame, the trolley being designed to be nestedwith a like trolley where a front portion of one said trolley is inoverlapping relation with a rear portion of another said trolley, andwherein the trolley further includes lifting means which is operative tocause the wheels of the front wheel assembly of the one trolley to belifted off the ground during nesting of the one trolley with said othertrolley.

A trolley according to the above form has significant advantage. Thetrolley may exhibit improved manoeuvrability by having a fixed wheelassembly at the front wheel assembly according to any form describedabove. Further, the manoeuvrability of a train of nested trolleys inaccordance with the invention is also significantly easier to manoeuvreby virtue of the lifting means which disengages each of the front wheelsassemblies of the nested trolleys off the ground. With this arrangement,only the front wheel assembly of the front trolley in the train is inengagement with the ground. Therefore the train includes one fixed frontwheel assembly with the remaining wheels being part of the individualtrolleys rear wheels which are preferably casters. This provides anarrangement which is easier to manoeuvre than traditional trains ofnested shopping trolleys which includes only swivelling casters.Further, by virtue of the fact that the front wheel assemblies of thenested trolleys is disengaged from the ground, the number of wheelsactually in contact with the ground in any train is significantlyreduced which further improves the manoeuvrability of the train ofnested trolleys.

In one form, the lifting means is in the form of a camming surfacearranged to engage a complementary surface on the like trolley duringnesting. Through that engagement, the wheels on the front wheel assemblyof the one trolley is caused to move off the ground.

This camming arrangement may be located on any suitable part of thetrolley such as on the basket, or trolley frame.

In an alternative form, the front wheel assembly may be operative tomove out of engagement with the ground using a different mechanism asthe lifting means. For example, the wheel assemblies may be pivotablefrom an extended to a retracted configuration, and wherein on nesting ofthe one trolley with the like trolley, the front wheel assemblies may becaused to move from their extended position to their retracted position.

In yet a further aspect, the present invention relates to theretrofitting of existing shopping trolleys so as to provide the enhancedmanoeuvrability afforded by the shopping trolleys of the earlier aspectsof the invention. In particular, in one aspect the invention is directedto retrofitting existing shopping trolleys so as to incorporate thelifting means. This aspect aims to use techniques which are inexpensivewhich thereby will not be prohibitively expensive to retrofit hundredsof shopping trolleys in a typical supermarket.

In accordance with this further aspect, the invention relates to acamming device for a trolley, the camming device including a bodyincorporating a camming surface, and attachment means operative to fixthe camming device to said shopping trolley, the trolley including abasket incorporating a rear gate and the trolley being designed so as tobe able to adopt a nested configuration with a like trolley, where thebasket of one trolley locate through the rear gate of another trolley sothat when nested, a substantial portion of the basket of the one trolleyis disposed within the basket of the like trolley, and wherein in use,when the camming device is fixed to the trolley, the camming surface isoperative to engage the other trolley in the nested configuration so asto lift the one trolley as it is moved into the nested configuration soas to cause the front wheel assembly to disengage the ground.

In one form, the camming device includes an elongate member havingopposite ends, the member being shaped so as to form a camming surfaceintermediate the ends, and wherein the attachment means comprisesengagement elements located at each end which are operative to be fixedto the trolley.

In one form, the camming device is operative to be secured to the basketof the trolley and the engagement means is preferably in the form ofeyelets which are operative to engage respective wire bars of thetrolley basket. The advantage of this arrangement is that the cammingdevice is inexpensive, and the method of attachment can be easilyperformed by providing the eyelets in partially open form on respectivewire bars of the basket and merely clinching them to securely affix themin place.

In yet a further aspect, the present invention relates to a method ofretrofitting a trolley to incorporate a camming device which includesthe steps of providing a camming device in any form described above, andsecuring the camming device to the trolley in a position so that whenthe trolley is moved into a nested configuration with a like trolley,the camming device on one of the trolleys is operative to engage theother of the trolley in the nested configuration so as to cause the onetrolley to be lifted so that the front wheels disengage the ground inthe nested configuration.

It is to be appreciated that the trolley including the lifting means inaccordance with these aspects of the invention is ideally suited to beused in conjunction with a trolley including the front wheel assemblywith a fixed wheel assembly in accordance with the earlier aspects ofthe invention. Alternatively, it may be used with trolleys having otherarrangements of front wheel assemblies, whether they include a fixedwheel or not.

In yet a further aspect, the invention relates to methods and systems tomodify an existing pair of caster wheel assemblies so as to provide afixed axle wheel arrangement using simple and inexpensive techniques.

Accordingly, in this aspect, there is disclosed herein apparatus adaptedto secure a pair of casters mounted on a trolley body againstswivelling, each said caster having a wheel mounted on an axle passingthrough a yoke which is in turn rotatably mounted on said trolley body,said apparatus including:

-   -   a rigid elongate member adapted to pass through an aperture        provided in each said yoke such that the rotation axes of said        wheels are substantially coaxial, and    -   means for fixedly securing said elongate member to said yokes.

Typically said elongate member has a circular cross-section toward eachend therefor and is adapted to replace the axle of each of said casters.

Typically said securing means includes a pair of nuts each respectivelyadapted to thread onto a threaded portion provided at each respectiveend of said elongate member so as to abut the respective said yoke.

Typically said securing means includes means for abutting each said yokeon an opposing side thereof to the associated elongate member end.

Preferably said abutting means includes a pair of circlips each adaptedto be received in a groove provided in said elongate member, each saidgroove being positioned such that, in use, each said circlip abuts asaid frame.

Preferably said abutting means includes a pair of shoulders each definedby a change in cross-section of said elongate member. Alternatively theapparatus further includes a sleeve locatable over the elongate memberand wherein opposite ends of the sleeve provides said abutting means.

There is further disclosed herein a method of securing a pair of castersmounted on a trolley body against swivelling, each said caster having awheel mounted on an axle passing through a yoke which is in turnrotatably mounted on said trolley body, said method including the stepsof:

-   -   providing an aperture in the yoke of each of said caster wheel        assemblies;    -   positioning each said caster such that the rotation axes of said        wheels are substantially co-axial;    -   passing a rigid elongate member through each said aperture so as        to maintain said rotation axes in a substantially co-axial        relationship, and    -   fixedly securing said elongate member to said yokes.

Typically said elongate member is circular in cross-section towards eachend thereof and said step of providing an aperture in each yoke isachieved by removing the axle of each said caster, said elongate memberreplacing said axles so as to provide said axes of rotation of saidwheels.

There is still further disclosed herein a method of modifying thehandling characteristics of a shopping trolley having four caster wheelassemblies mounted on the body thereof, said method including the stepof securing either the front or rear pair of caster wheels againstswivelling according to the above disclosed method.

There is still further disclosed herein a trolley modified by the abovemethod.

Accordingly, the present invention provides a novel trolley andassociated methods of modification of existing trolleys, which in someaspects have the advantage of the fixed front wheels, but have improvedmanoeuvrability, and which may be inexpensively retrofitted to beincorporated into existing trolleys.

BRIEF DESCRIPTION OF THE DRAWINGS

It is convenient to hereinafter describe embodiments of the presentinvention with reference to the accompanying drawings. It is to beappreciated that the particularity of the drawings and the relateddescription is to be understood as not superseding the generality of thepreceding broad description of the invention.

In the drawings:

FIG. 1 is a side view of a shopping trolley according to a firstembodiment of the invention;

FIG. 2 is a front elevation view of a front wheel assembly of thetrolley of FIG. 1;

FIGS. 3A and 3B are detailed side elevations of the front wheel assemblyof FIG. 2;

FIG. 4 is a front elevation view of a front wheel assembly for a trolleyaccording to a second embodiment of the invention;

FIG. 5 is a detailed view of the camming device in the trolley of FIG.1;

FIG. 6 is a side view of the trolley of FIG. 1 in a nestedconfiguration;

FIG. 7 is a front elevation view of a pair of casters mounted on atrolley body and modified with the apparatus of a further embodiment ofthe invention;

FIG. 8 is a side elevation view of the casters of FIG. 7;

FIG. 9 is a side elevation view of a pair of casters modified in analternative manner;

FIG. 10 is a front elevation view of an elongate rod of the apparatus ofFIG. 7; and

FIG. 11 is a front elevation view of an elongate rod of the apparatus ofFIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A shopping trolley 10 includes a frame 11 from which the front wheelassembly 12 and a rear wheel assembly 13 is mounted. A wire basket 14 issupported on the frame and includes a handle 15 and rear gate 16. As istypical in shopping trolleys, the rear wheel assembly includes a pair ofswivel casters 17 mounted at each back corner of the frame 11.

As best illustrated in FIGS. 2, 3A and 3B, the front wheel assembly 12include a pair of swivel casters which are mounted on respective frontcorners of the frame 11. Each caster 18 includes a yoke 19 which isarranged to rotate about a king pin 20 allowing the casters 18 to rotateabout respective first axes 21. Caster wheels 22 are mounted on therespective yokes 19 and are rotatable about respective second axes 23which are transverse to their respective first axes 21.

To provide control to the trolley, the front wheel assembly 12 include acentre fixed wheel assembly 24 which is mounted to the trolley frame 11.In the illustrated form, the fixed wheel assembly 24 is displacedrearwardly of the front wheel assembly and is secured by a bracket 25which is secured to the frame 11. In the illustrated form, the fixedwheel assembly 24 is secured to the bracket 25 by locating a threadedbolt 26 through an aperture in the bracket 25 which is secured in placeby a nut 27. It is to be appreciated that other forms of fixing could beemployed as will be appreciated by those skilled in the art. Further,the fixed wheel assembly 24 may be located in line with the casters 18if there is adequate clearance to allow those casters to swivel, ordisposed slightly forward.

The fixed wheel assembly 24 is in the form of a non swivelling casterand includes a yoke 28 and a wheel 29 which is mounted to the yoke 28and rotatable about an axis of rotation 30.

FIGS. 3A and 3B are a side elevation of the front wheel assembly ofFIG. 1. As can be seen, in this arrangement, the fixed wheel assembly 24is secured rearward of the line of the casters 18. In addition, thefirst axes 21 of the casters 18 are each inclined to the vertical (V).This is achieved in the illustrated embodiment by having the trolleyframe 11 slightly inclined forwardly through having larger casters onthe rear wheel assembly than the front wheel assembly. Further, asillustrated in FIG. 3A, the centre line (P) of each wheel 22 isdisplaced from its first axis 21. As such, the caster wheels 22 aredesigned to move in an arc around their first axes 21. Because eachfirst axis 21 is inclined to the vertical, the plane in which the casterwheels will move on swivelling is inclined to the horizontal plane.

In the illustrated embodiment, the first axes 21 of the casters 18 areinclined in the forward direction of the trolley. As a result of thisorientation, when the casters 18 are in a trailing position for forwardmovement of the trolley as illustrated in FIG. 3A, the caster wheels 22are at the highest point of their arc. Further, the fixed wheel 29 ofthe trolley is designed so that it is aligned with the height of thecaster wheels at this point so that both the caster wheels 18 and thefixed wheel 29 are engaging with the surface 200 on forward movement ofthe trolley.

When the caster wheels 100 swivel about their first axes 21 away fromthe trailing position as shown in FIG. 3A, the distance between thecaster wheel centres and the trolley frame 11 increases, which causesthe trolley frame 11 to lift. This, in turn, causes the fixed wheel 29to move off the ground as illustrated in FIG. 3B. This arrangement hassignificant practical benefit as it enables the fixed wheel 30 to assistin fully maintaining control of the trolley in the forward direction butstill enables easy sideways movement of the trolley if required.

Accordingly, front wheel assembly 12 has the advantages of a centralisedfixed wheel for pivoting and manoeuvrability of the trolley particularlyfor forward movement, but which still can provide adequate stability tothe trolley to prevent tipping. Further, the design of the front wheelassembly allows unimpeded sideways movement by creating a system wherethe fixed wheel can disengage the ground on certain orientations of thefront casters.

FIG. 4 illustrates a modified version of the front wheel assembly 12.Again the main principal of the wheel assembly 12 is to provide acentralised fixed wheel between the front casters 18 to facilitatemanoeuvrability of the trolley. In this arrangement however, the casters18 are modified as part of the installation of the fixed wheel assembly31.

In particular in the arrangement of FIG. 4, the caster wheels 22 areremoved from their respective yoke 19 and those yokes are securedagainst swivelling by a rigid elongate member 32. Outrigger wheels 34are included in the modified assembly 12 and the caster wheels 22 formpart of the fixed centre wheel assembly 31.

In constructing the front wheel assembly 12, an aperture is provided ineach of the yokes 19 through which the elongate member 32 may pass whenthe casters 18 are positioned with the second axis 23 substantiallycoaxial. Individual axle in each caster 18 is removed so that theelongate member is passed through the axle apertures 35 provided in therespective yokes 19. In the illustrated form, the elongate member 32includes a threaded portion 36 at each opposite end for receiving a nut37 to secure the elongate member 32 in place.

In conjunction with installing the elongate member 32 to actually fixthe yokes 19, the caster wheels 22 are removed from the yokes 19 and aremounted on the member 32 intermediate the casters 18. Spaces 38 which inthe illustrated form are sleeves of metal or plastic, are disposed onthe elongate member to locate the caster wheels 22 in their centralposition. In this way, the elongate member which has a circular crosssection provides the axis of rotation for the wheels 22 which are nowcentrally fixed. It is to be appreciated that other suitable spaces,such as circlips or the like may be used.

In addition, outrigger wheels 34 are installed in the yokes 19 toprovide additional stability to the trolley. These outrigger wheels aresmaller than the casters 22 and are therefore only designed to come incontact with the ground should the trolley 10 tip.

The trolley 10 in any form described above is designed to nest with alike trolley 10′ as best shown in FIG. 6. Specifically the trolleybasket 14 with the pivoting rear gate 16, tapers towards its front. Withthis arrangement, the trolley 10 is able to nest with the like trolley10′ with the basket 14 locating through the rear gate 16′ of the liketrolley 10′ so that when nested, the basket 14 of the trolley isdisposed within the basket 14′ of the like trolley.

The trolley 10 includes a camming device 40 which is mounted to thebasket 16. The device 40 includes an elongate metal member 41 which isarcuately shaped so as to form a cam surface 42 over its mid region.Each end (44,46) of the member 41 includes rolled over edges to formeyelets 45, 46. Wire bars 47 of the basket 16 are operative to locatewithin the eyelets 45, 46 so as to secure the camming device to thebasket.

To retrofit the camming device to the shopping trolley 10, the member 41is provided with the eyelets partially opened so as to enable respectivebars 47 of the basket 14 to be received in the eyelets whereafter theyare secured in place by clinching the respective eyelets to close them.

In fitting the camming device 40 in place, the shopping trolley 10 maybe provided with a single device, or multiple devices may be provided.Further, in the illustrated form, the camming devices 40 extendsdownwardly from a bottom surface 48 of the basket 14. The advantage ofthis arrangement is that it places the camming device out of the way anddoes not reduce the volume of the material which can be provided withinthe trolley basket 14. Further, the formation of eyelets 45,46 at theend of the member provides a convenient safety edge to the cammingdevice 20 which is unlikely to provide a pinch point or sharp edge whichcould otherwise catch on material placed in the basket 14.

The inclusion of the camming device 40 is designed to cause a shoppingtrolley 10′ when moved into a nested configuration to lift to asufficient degree to cause the front wheel assembly 12′ of nestedtrolley 10′ to disengage the ground. This is achieved by the cammingsurface 22 moving into engagement with the bottom surface 48′ of thetrolley basket 14′. By virtue of this engagement of surfaces, thetrolley 10′ is caused to lift disengaging the front wheel assemblies 12′from the ground. It is to be appreciated that the camming device 40could be disposed to extend upwardly from the base of the trolley basket14 and achieve the same result when a trolley is moved into a nestingconfiguration.

When in this nested configuration, the lifting of the front wheelassemblies 12′ ensures that these assemblies do not impede themanoeuvrability of a train of the trolleys in a nested configuration.

FIGS. 7 to 11 disclose yet a further form of modifying the casters ofthe front wheel assembly 12. This embodiment has many similarities tothe embodiment shown with reference to FIG. 4 with the exception thatthe modified trolley does not include a central fixed wheel assembly.

As best shown in FIG. 7, the wheels 22 of the casters 18 are securedagainst swivelling by a rigid elongate member 50. An aperture isprovided in each of the yokes 19 through which the elongate member 50may pass when the casters 18 are positioned with the rotation axes ofthe wheels 22 substantially co-axial. In one embodiment, the axles 51 ofeach wheel are removed so that the elongate member is passed through theaxle apertures 52 provided in the yokes 19. The elongate member 50,whose ends have a circular cross-section, thus replaces the axles so asto provide the axes of rotation of the wheels 22, ensuring that the axesof rotation are co-axial. The elongate member 50 is then fixedly securedto the yokes 19.

The elongate member 50 of this embodiment, which is in the form of acircular rod, is best depicted in FIG. 10. A threaded portion 53 isprovided at each opposing end of the elongate rod 50 for receiving a nut54. A nut 54 is threaded onto each threaded portion 53 once the elongaterod has passed through the apertures 52. Each nut 54 is tightened ontothe threaded portion 53 until it abuts the associated yoke 19 adjacentthe elongate frame end. A washer 55 is typically provided between thenut 54 and yoke 19. Fastening the nuts 54 onto each end of the elongaterod 50 thus fixedly secures the elongate rod 50, with each end securedto its respective yoke 19. The rotation axes of the wheels 22 are thusfixed in the substantially co-axial relationship.

To further secure the elongate rod 50, means may be provided to abuteach yoke 19 on an opposing side thereof to the associated elongatemember end. In the first embodiment this means is provided by circlips56. The circlips 56 each abut an inner fork 62 of yoke 19, whilst a nut54 abuts an outer fork 63 on the opposing side of the yoke 19. With eachyoke 19 being abutted on opposing sides, the securing thereof is morerobust. Each circlip 56 is received in a circumferential groove 57provided in the elongate member 50 at a position adjacent to the innerfork 62 of each yoke 19 when the elongate member 50 is in position.

An alternative elongate member 58 is depicted in FIG. 11. Like elongatemember 50 it is provided with threaded portions 59 for receiving nuts57. However, in place of the grooves 57 for receiving circlips,shoulders 60 are provided at positions corresponding to adjacent theinner fork 62 of each yoke 19. The shoulders 60 are formed by a changein cross-section of the elongate member 58 from a larger cross-sectionin a central region to smaller cross-sections at outer regions of theelongate member. These shoulders 60 thus abut the inner forks 62 whenthe elongate member 58 is in position, helping to further secure theyokes 19 against swivelling. Rather than providing integral shoulders60, the same abutment effect could be achieved by sliding a sleeve overa constant cross section elongate member, the sleeve having a lengthapproximating the distance between the inner forks 62.

Rather than pass either of the alternate elongate members 50, 58 throughthe aperture 52 usually occupied by the wheel axles 51, a separateaperture 61 may be provided on each yoke 19 away from the wheels 22 asdepicted in FIG. 9. The elongated rod 50, 58 is thus passed through theapertures 61 and secured to the yokes 19 in the manner discussed above.The original axles 51 remain in place.

Other alternative forms of securing the elongate member 50, 58 to theframes will be appreciated by the person skilled in the art. One suchalternative form would be the use of circlips to replace the nuts 54abutting the outer forks 63.

It is preferred that the modified wheel assemblies to include a fixedwheel assembly in any form detailed above is installed on the frontwheel assembly 12 as the provision of an elongate rod spanning the rearcasters 17 or the presence of a centre fixed wheel may act as a barrierto nesting of trolleys one inside the other. The elongate member orfixed wheel assembly may jamb against the front of a trolley beingstacked into the back of a trolley so modified. It is also preferredthat the wheels 22 are positioned such that their rotation axes areco-axial, however slight misalignment, including a slight toe-in ortoe-out of the wheels will still provide effective manoeuvrability.

It is to be appreciated that variations and/or modifications may be madeto the parts previously described without departing from the spirit orambit of the invention.

1. A trolley comprising: a trolley frame; front and rear wheelassemblies, one of the front and rear wheel assemblies including a pairof casters; each of the pair of casters having a first axis and a secondaxis transverse to the first axis and including a yoke mounted to thetrolley frame in a manner that allows the caster to swivel about thefirst axis, and a caster wheel mounted to the yoke so as to be rotatableabout the second axis, each of the pair of casters being operative toadopt a first orientation for forward travel of said trolley; and afixed wheel assembly located between said pair of casters, said fixedwheel assembly including at least one wheel which has an axis ofrotation which is orientated so that said fixed wheel assembly assistsin maintaining directional control of said trolley in its forwardtravel, wherein the trolley frame is caused to lift on swiveling of thecasters from their first orientation by having the centre of the casterwheels radially displaced from their first axes and having the firstaxes inclined to the vertical and extending rearwardly of the trolleyand the at least one wheel of the fixed wheel assembly is positioned toengage the ground when the castors are in their first orientations andto be off the ground on swivelling of the casters about their first axesfrom their first orientations.
 2. A trolley according to claim 1,wherein the fixed wheel assembly is disposed between the casters.
 3. Atrolley according to claim 1, wherein the wheel assembly including thepair of casters is the front wheel assembly.
 4. A trolley according toclaim 3, wherein the wheel of the fixed wheel assembly is aligned withthe casters of the front wheel assembly.
 5. A trolley according to claim3, wherein the fixed wheel assembly is displaced either forward orrearward of the casters of the front wheel assembly.
 6. A trolleyaccording to claim 1, wherein the other of the front and rear wheelassemblies also includes a pair of casters, each caster having a firstaxis and a second axis transverse to the first axis and including a yokemounted to the trolley frame in a manner that allows the caster toswivel about the first axis, and a caster wheel mounted to the yoke soas to be rotatable about the second axis, each of the pair of casters ofthe other wheel assembly being operative to adopt a first orientationfor forward travel of said trolley.
 7. A trolley according to claim 1,wherein the fixed wheel assembly is the form of a fixed caster includinga yoke mounted to the trolley frame, and a caster wheel rotatablymounted to the yoke.
 8. A trolley according to claim 1, wherein thetrolley is designed to be nested with another said trolley, wherein thefront portion of one trolley is in overlapping relation with the rearportion of the other trolley, and wherein the trolley further compriseslifting means which is operative to cause the wheels of the front wheelassembly of the one trolley to be lifted off the ground on nesting ofthe two trolleys.
 9. A trolley according to claim 8, wherein the liftingmeans is in the form of complementary surfaces arranged to interengageduring nesting of the trolleys.
 10. A trolley according to claim 9,further comprising a camming device which includes a camming surface,the camming device being secured to the trolley so that the cammingsurface forms one of the complementary surfaces and engages a surface ofthe other trolley on nesting of the trolleys.
 11. A trolley according toclaim 10, wherein the trolley further comprises a basket having a reargate, and wherein on nesting, the basket of the one trolley locates inthe basket of the other trolley through the rear gate, and wherein thecamming surface is positioned so as to engage a surface of the basket tocause lifting of the one trolley.
 12. A trolley according to claim 11,wherein the camming device is mounted on a base surface of the basketand projects downwardly therefrom.
 13. A trolley according to claim 11,wherein the camming device is mounted to a base of the basket andprojects upwardly therefrom.
 14. A trolley according to claim 10,wherein the camming device comprises an elongate member having oppositeends and being profiled to form the camming surface intermediate theends, the member further comprising engagement elements located at eachend which are arranged to be fixed to the basket of said trolley.
 15. Atrolley according to claim 14, wherein the basket of the trolley isformed from wire mesh and the engagement elements are in the form ofeyelets which are operative to engage respective wire bars of thetrolley basket.
 16. A trolley comprising: a trolley frame; a baskethaving a rear gate mounted on the trolley frame; front and rear wheelassemblies, the front wheel assembly including a pair of casters; eachof the pair of casters having a first axis and a second axis transverseto the first axis and including a yoke mounted to the trolley frame in amanner that allows the caster to swivel about the first axis, and acaster wheel mounted to the yoke so as to be rotatable about the secondaxis with the centre of the caster wheel being radially displaced fromthe first axis, each of the pair of casters being operative to adopt afirst orientation for forward travel of said trolley; a fixed wheelassembly located between said pair of casters, said fixed wheel assemblyincluding at least one wheel which has an axis of rotation which isorientated so that said fixed wheel assembly assists in maintainingdirectional control of said trolley in its forward travel; and a cammingdevice which includes a camming surface; wherein the trolley is arrangedto be nested with another said trolley where the basket of one trolleylocates in the basket of the other trolley through the rear gate andwherein the camming surface is positioned so as to engage a surface ofthe basket of said other trolley to causing lifting of the one trolley.17. A trolley according to claim 10, wherein the camming devicecomprises an elongate member having opposite ends and being profiled toform the camming surface intermediate the ends, the member furthercomprising engagement elements located at each end which are operativearranged to be fixed to the basket of said trolley.
 18. A trolleyaccording to claim 14, wherein the basket of the trolley is formed fromwire mesh and the engagement elements are in the form of eyelets whichare operative to engage respective wire bars of the trolley basket.